A2Sb2SO4F6 (A = NH4+, Na+): Two Sulfate Fluoride Crystals Exhibiting Enhanced Birefringence Driven by Stereochemically Active Antimony (III)

Abstract

Two antimony sulfate fluoride birefringent crystals, (NH4)2Sb2SO4F6 and Na2Sb2SO4F6 were successfully synthesized by mild aqueous solution method. Compared with the alkali metal sulfates, they exhibit enhanced optical anisotropy with the birefringence of 0.055 and 0.100 at 1064 nm, respectively, which mainly depends on the stereochemically active [SbO2F3] and [SbOF3] polyhedra.